Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

16. Conjugated Systems

Conjugation Chemistry

Organic Chemistry

16. Conjugated Systems

Conjugation Chemistry

Previous problemNext problem

1:15 minutes

Problem 40h

Textbook Question

Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.
(h)

Verified step by step guidance

Step 1: Analyze the structure for conjugation. Conjugation occurs when there is a series of alternating single and double bonds, allowing for delocalization of π-electrons across the molecule. In this structure, observe the aromatic rings and the extended conjugation involving sp2 hybridized atoms.

Step 2: Identify the functional groups. The molecule contains a hydroxyl group (-OH) and a nitro group (-NO2). The nitro group is an electron-withdrawing group, which can influence the electronic properties of the conjugated system.

Step 3: Determine the extent of conjugation. Mark the series of continuous sp2 hybridized atoms in the aromatic rings and any other conjugated systems. Extended conjugation increases the likelihood of the molecule absorbing visible light and appearing colored.

Step 4: Consider the electronic effects of the substituents. The nitro group can pull electron density away from the conjugated system, potentially shifting the absorption spectrum into the visible range. This effect can make the molecule appear colored.

Step 5: Predict whether the molecule is likely to be colored. Based on the extended conjugation and the presence of electron-withdrawing groups, the molecule is likely to absorb visible light and exhibit color. Highlight the conjugated system to confirm the prediction.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Conjugation

Conjugation refers to the overlap of p-orbitals across adjacent sp2 hybridized atoms, allowing for the delocalization of π electrons. This delocalization stabilizes the molecule and can lead to the absorption of visible light, resulting in color. The more extensive the conjugation, the lower the energy gap between the ground and excited states, which can shift the absorption into the visible spectrum.

Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can form sigma bonds. In organic compounds, sp2 hybridization involves one s and two p orbitals, creating three equivalent sp2 orbitals and leaving one p orbital unhybridized. This unhybridized p orbital is crucial for forming π bonds and contributes to the conjugation in colored compounds.

Color and Light Absorption

The color of a compound is determined by the wavelengths of light it absorbs. When a molecule absorbs light, it promotes electrons from a lower energy level to a higher one. If the energy difference corresponds to visible light, the compound will appear colored. The specific wavelengths absorbed depend on the extent of conjugation and the electronic structure of the molecule.

Watch next

Master Definition of Conjugation with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

How many 𝝅 electrons are involved in the conjugated system for each of the following molecules?

(a)

Textbook Question

Identify the isoprene units in the terpenes shown. In cross-linked or ring-containing terpenes, linkages can be formed between more than just C₁ and C₄ of isoprene.

(a)

Textbook Question

Phenolphthalein is an acid–base indicator that is colorless below pH 8 and red above pH 8. Explain briefly why the first structure is colorless and the second structure is colored.

Textbook Question

Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.

(g)

Textbook Question

Determine whether each structure is likely to be colored or not. For those that you predict to be colored, indicate the extended conjugation by marking the series of continuous sp² hybridized atoms.

(i)

Textbook Question

a. How many MOs does 1,3,5,7-octatetraene have?

b. What is the designation of its HOMO (c1, c2, etc.)?

c. How many nodes does its highest energy MO have between the nuclei?

Textbook Question

Why is this not a viable representation of the ψ₂, molecular orbital of buta-1,3-diene?

Textbook Question

The ψ₂ molecular orbital for octa-1,3,5,7-tetraene is shown. Draw ψ₃.

<IMAGE>

Show more practices